Total expenditures in a country $($in billions of dollars$)$ are increasing at a rate of $f(x)=8\mathrm{.}42x+87\mathrm{.}14,$ where $x=0$ corresponds to the year $2000.$ Total expenditures were $$1585\mathrm{.}32$ billion in $2002.$

a$.$ Find a function that gives the total expenditures $x$ years after $2000.$

b$.$ What will total expenditures be in $2012?$

a$.$ What is the function for the total expenditures?

$F(x)=$

$($Simplify your answer. Use integers or decimals for any numbers in the expression.$)$